This invention relates generally to medical devices, and more particularly to pulse generating systems.
Implantable pulse generators (e.g., pacemakers, implantable cardioverter/defibrillators) are integrated highly sophisticated electro-mechanical systems. They typically comprise at least one implantable cardiac lead coupled to a pulse generating device. The implantable cardiac leads serve to physically and electrically connect the pulse generating device, including the electronic circuitry housed within the device, to pacing electrodes positioned on the implantable cardiac lead. The implantable cardiac lead, therefore, acts as a tether to connect the pacing electrodes on the cardiac lead to the implantable pulse generating device.
Implantable cardiac leads typically include at least one pacing electrode, a lead conductor, lead insulation, and a lead connector. When one pacing electrode is present on the implantable cardiac lead, it is typically placed at the distal end of the lead. The lead conductor physically and electrically couples the pacing electrode to the electronic circuitry of the pulse generator. The lead conductor serves to conduct pacing level energy pulses from the electronic circuitry to the pacing electrode, and to conduct cardiac signals sensed by the pacing electrode to the electronic circuitry.
The lead conductor is housed within the lead insulation. The lead insulation electrically isolates the lead conductor, allowing the pacing level energy pulses from the pulse generator to be delivered to the pacing electrode and cardiac signals from the pacing electrode to be delivered to the electronic circuitry of the pulse generator. The lead connector also serves to physically couple the implantable cardiac lead to the housing of the pulse generator. Thus, the current state of the art for implantable pulse generators is to use the lead conductor to pass electrical pacing pulses to the pacing electrode when delivering pacing pulses to the heart.
The size of implantable cardiac leads is often a limiting factor in where the implantable cardiac lead can be positioned within the heart. Typically, implantable cardiac leads have been implanted through the venous side of the circulatory system, with the distal end of the cardiac lead being positioned in either the right ventricle or right atrium. Implantable cardiac leads can also be positioned adjacent the left atrium or left ventricle by placing the lead in the coronary sinus or great cardiac vein. Regardless of the location, the pacing electrodes are always tethered to the pulse generator by cardiac lead. As a result, sites available for cardiac pacing by implantable cardiac leads are limited. Thus, a need exists whereby implanted electrodes for delivering electrical energy to cardiac tissue need not be constrained by the presence of a cardiac lead.
The present subject matter removes the limitation of the pacing electrode being coupled, or tethered, to the implantable cardiac lead. In one embodiment, there are provided self-contained electrodes which are adapted to receive at least one signal from a transmitter. In response to receiving the at least one signal, the self-contained electrodes generate and deliver an electrical energy pulse. In one embodiment, the electrical energy pulses are pacing level energy pulses. Thus, the present subject matter allows for the physical connection between the implantable cardiac lead and the pacing electrode to be severed. By severing the physical connection between the implantable cardiac lead and the pacing electrode, the self-contained electrodes of the present subject matter are able to be placed at any number of locations within the cardiac tissue without the limiting constraint of the traditional implantable cardiac lead.
In one embodiment, present subject matter provides an implantable electrode, where the electrode comprises a first piezoelectric element which converts mechanical energy into electrical energy, and a cathode and an anode, where electrical energy generated by the first piezoelectric element causes a pacing level energy pulse to be delivered between the anode and the cathode. In one embodiment, the mechanical energy for stimulating the piezoelectric element originates from a source external to the implantable electrode. In one embodiment, the external source is from a transmitter that is located on, or integrated into, either a cardiac lead and/or the implantable pulse generator.
In one embodiment, the implantable electrode includes an implantable housing into which is integrated the first piezoelectric element. The housing also includes an anode and a cathode positioned the peripheral surface of the housing. The housing also contains pacing control circuitry, which is coupled to the first piezoelectric element, the anode and the cathode. In one embodiment, the pacing control circuitry serves to receive the electrical energy generated by the first piezoelectric element and control the delivery of pacing level energy pulse between the anode and the cathode.
In an additional embodiment, the implantable electrode can further include a potential energy source (e.g., an electrochemical cell) which supplies at least a portion of the energy necessary to pace the cardiac tissue. In addition to the potential energy source, the pacing control circuitry can further include a switch, where the switch is operated by the electrical energy generated by the first piezoelectric element. In one embodiment, the switch is activated so as to deliver a pulse between the anode and cathode when the switch receives electrical energy generated by the first piezoelectric element.
In an alternative embodiment, the implantable electrode can further include a second piezoelectric element which converts mechanical energy into electrical energy. When a first and second piezoelectric element are present, each element is selected to resonate in a different frequency range, so that the first piezoelectric element resonates at a first frequency range and the second piezoelectric element resonates at a second frequency range. The implantable electrode further includes both the switch and a capacitor. In one embodiment, the switch is coupled to the first piezoelectric element, the second piezoelectric element, the anode and the cathode, and the capacitor is coupled to the switch.
Electrical energy is generated by the first piezoelectric element when a first transmission at the first frequency range resonates the first piezoelectric element and electrical energy is generated by the second piezoelectric element when a second transmission at the second frequency range resonates the second piezoelectric element, where the electrical energy is stored in the capacitor. The switch is then used to cause the pacing level energy pulse to be delivered between the anode and the cathode when a predetermined pulse signal is detected. In one embodiment, the predetermined pulse signal is a predetermined frequency change in the first frequency range. Alternatively, the predetermined pulse signal is a predetermined frequency change in the first and second frequency ranges.
In an alternative embodiment, the pacing control circuitry includes a switch, where the switch is operated by the electrical energy generated by the first piezoelectric element, and a potential energy source, where the potential energy source is coupled to the switch and supplies electrical energy to be delivered between the anode and the cathode once the first piezoelectric element provides electrical energy to activate the switch.
These and other features and advantages of the invention will become apparent from the following description of the preferred embodiments of the invention.